HTML table column of equal size

With the below code, I get the columns size being different (esp the last column is small) I would like to have all the three columns to be of same size.Thanks.

<html>
<body>
<h4>Two rows and three columns:</h4>
<table border="1" width="100%" height="400" align="top">
<tr style="height: 1">
  <td>
   <table width="100%" border="2" height ="100" align="top">
     <tr>
       <td>1-1</td>
       <td>1-2</td> 
     </tr>
     <tr>
       <td>1-3</td>
       <td>1-4</td>
     </tr>
   </table>
 </td> 
  <td>
   <table width="100%" border="2" height ="100" align="top">
     <tr>
       <td>2-1</td>
       <td>2-2</td> 
     </tr>
     <tr>
       <td>2-3</td>
       <td>2-4</td>
     </tr>
   </table>
<td>
   <table width="100%" border="2" height ="100" align="top">
     <tr>
       <td>3-1</td>
     </tr>
     <tr>     
       <td>3-2</td>
     </tr>
   </table>
 </td> 
</tr>
<tr style="vertical-align: top">
 </td> 
  <td>
   <table width="100%" border="2" height ="100">
     <tr>
       <td>4-1</td>
       <td>4-2</td> 
     </tr>
     <tr>
       <td>4-3</td>
       <td>4-4</td>
     </tr>
</table>
 <td>
   <table width="100%" border="2" height ="100">
     <tr>
       <td>5-1</td>
       <td>5-2</td> 
     </tr>
     <tr>
       <td>5-3</td>
       <td>5-4</td>
     </tr>
   </table>
<td> 
   <table width="100%" border="2" height ="100">
     <tr>
       <td>6-1</td>
     </tr>
     <tr>
       <td>6-3</td>
     </tr>
   </table>
</body>
</html>

Solution

Insert a colgroup element in your table:

<table>
  <colgroup>
    <col style="width: 33%" />
    <col style="width: 33%" />
    <col style="width: 33%" />
  </colgroup>
  <tr>
...
  </tr>
</table>